What is the value of the decay constant of a compound having a half-life time $T_{1/2} = 2.95 \text{ days}$?

The half-life of radium is $1580 \ yrs$. Its average life will be:

The half-life of $_{38}^{90}Sr$ is $20 \text{ years}$. If a sample having an initial activity of $8000 \text{ dis/min}$ is taken,what would be its activity after $80 \text{ years}$?

The half-life of the radioactive isotope tritium $(_1^3H)$ is $12.3 \ years$. If the initial amount of tritium is $32 \ mg$,how many milligrams will remain after $49.2 \ years$ (in $mg$)?

Assuming $1 \, \mu g$ of trace radioactive element $X$ with a half-life of $30 \ years$ is absorbed by a growing tree. The amount of $X$ remaining in the tree after $100 \ years$ is $n \times 10^{-1} \, \mu g$. Find the value of $n$. $[Given : \ln 10 = 2.303 ; \log 2 = 0.30]$

$A$ radioactive sample is emitting $64$ times more radiation than the non-hazardous limit. If its half-life is $2 \ hr$,after what time will it become non-hazardous? $(hr)$